In Vivo Efficacy of Enabling Formulations Based on Hydroxypropyl-β-Cyclodextrins, Micellar Preparation, and Liposomes for the Lipophilic Cannabinoid CB2 Agonist, MDA7

Enabling formulations based on hydroxypropyl-β-cyclodextrins (HPβCD), micellar preparation, and liposomes have been designed to deliver the racemic mixture of a lipophilic cannabinoid type 2 agonist, MDA7. The antiallodynic effects of MDA7 formulated in these three different systems were compared after intravenous (i.v.) administration in rats. Stoichiometry of the inclusion complex formed by MDA7 in HPβCD was determined by continuous variation plot, electrospray ionization-mass spectrometry (ESI-MS) analysis, phase solubility, and nuclear magnetic resonance studies and indicate formation of exclusively 1:1 adduct. Morphology and particle sizes determined by dynamic light scattering and transmission electron microscopy show the presence of a homogeneous population of closed round-shaped oligolamellar MDA7 containing liposomes, with an average size of 117 nm [polydispersity index (PDI) <0.1]. Monodisperse micelles exhibited an average size of 15 nm (PDI 0.1). HPβCD-based formulation administrated in vivo was composed of two discrete particles populations with a narrow size distribution of 3 nm (PDI <0.1) and 510 nm (PDI <0.1). HPβCD-based formulation dramatically improved antiallodynic effect of MDA7 in comparison with the liposomes preparation. Through inclusion complexation and possibly formation of aggregates, HPβCD can enhance the aqueous solubility of lipophilic drugs, thereby improving their bioavailability for i.v. administration.